This invention relates to electro-optic apparatus.
Electro-optic apparatus, such as pyrometers, include an imaging system, such as including a lens, and a detector, such as a photodiode, on which the imaging system images external radiation. In some apparatus a dual-channel output is required, such as when the output is supplied to two different pieces of equipment, or for two different purposes, or where redundancy is required for safety reasons. In order to ensure that both outputs are equal, the two photodiodes must be mounted in such a way that both receive the same amount of radiation, that is, the area of the image that falls on one photodiode must be equal to that which falls on the other. Alternatively, the gain of the amplifiers receiving the outputs of the photodiodes can be adjusted to give equal outputs. If the radiation image is smaller than the area of the photodiodes or if the radiation is uneven over the direction at right angles to the line between the centers of the two photodiodes, will result in a change in output of the photodiodes but it generally affects both photodiodes to the same extent. If, however, the center of the radiation image is displaced in a direction with a component parallel to the line between the two photodiodes, this will generally result in an increase in the output from one photodiode and a reduction in the output from the other.